Remember, this is a 
guide. Slight bending of accepted practice should be OK.
Rim Width in Inches ------ Maximum Tire Width
6" ------ 9.50" Max
7" ------ 9.50"-10.50"
8" ------  10.50"-11.50"
8.5" ------ 10.50"-12.50"
10" ------ 12.50" and Up
P-Metric Size ------ Actual Tire Width ------ Actual Tire Height
15-inch rims    
205/70R15  ------    8.7 inches          ------   26.2 inches
215/75R15  ------    8.46 inches  ------    27.6 inches
235/75R15  ------    9.25 inches  ------    28.8 inches
265/70R15  ------    10.4 inches     ------ 29.6 inches
16-inch rims    
245/75R16     ------ 9.64 inches  ------    30.4 inches
285/75R16  ------    11.2 inches  ------    32.8 inches
315/75R16  ------    12.4 inches  ------    34.6 inches
395/70R16  ------    15.5 inches  ------    37.7 inches
17-inch rims    
235/65R17  ------    9.25 inches     ------ 29.5 inches
265/70R17     ------ 10.4 inches     ------ 31.6 inches
255/75R17     ------ 10.4 inches     ------ 32.0 inches
285/70R17     ------ 11.2 inches     ------ 32.7 inches
315/70R17     ------ 12.4 inches     ------ 34.3 inches
This is a nice guide too.
 
 